1. Field of the Invention
The present invention relates to a polarizing plate and a liquid crystal display device using the same, and more specifically to a polarizing plate provided with a pressure-sensitive adhesive layer and an optical compensation sheet, less causative of light-leakage due to thermally induced distortion, and a liquid crystal display device using such polarizing plate, capable of providing high-definition images.
2. Related Art
A liquid crystal display device comprises a polarizing plate and a liquid crystal cell. A TN-mode TFT liquid crystal display device, which is in the main stream at present, employs an optical compensation sheet (retardation film) disposed between the polarizing plate and the liquid crystal cell to achieve a high-displaying quality. However under severe conditions of use, the liquid crystal display device may produce unexpected retardation at the end portion thereof due to thermally induced distortion, and the retardation may cause frame-like light-leakage (elevation in transmittance at the end portion of the liquid crystal display device) in the black state.
Japanese Laid-Open Patent Publication No. 2001-264538 proposes an optical compensation plate less susceptible to changes in the retardation characteristics, having a pressure-sensitive adhesive layer provided to the retardation film, wherein product (Y) of photoelastic coefficient (m2/N) of a retardation film and modulus of elasticity (N/m2) of a pressure-sensitive adhesive layer satisfies Y<1.2×10−5. Japanese Laid-Open Patent Publication No. 2002-122739 proposes a predetermined polarizing plate moderated in the phenomenon of light-leakage, wherein a product of linear expansion coefficient of a polarizing plate protective layer and modulus of elasticity of a pressure-sensitive adhesive layer is 1.0×10−5 (° C.−1·MPa) or smaller. Japanese Laid-Open Patent Publication No. 2002-122740 proposes a polarizing plate less causative of in-plane non-uniformity, wherein a product of photoelastic coefficient of a polarizing plate protective layer and modulus of elasticity of a pressure-sensitive adhesive layer is 8.0×10−12 (m2/N·MPa) or smaller.